In the manufacture of packing containers from weblike, flexible packing laminate the laminate is given first a form, e.g. a tubular form, suitable for receiving the contents, whereupon the contents are introduced and individual packing containers are shaped and sealed through transverse sealing off and formprocessing of the packing laminate tube. This procedure and a machine for the realization of the same are described in greater detail in Swedish patent application No. 8202302-9, to which reference is made. The abovementioned type of packing container, which is generally used for milk, juice or other liquid foodstuffs, is provided with, among other things, an opening arrangement in the form of a tear-off cover strip (so-called pull-tab) placed over a prepared pouring opening. The opening arrangement here is formed while the packing laminate is in form of a web, and the opening arrangement including the cover strip, therefore, have to accompany the packing laminate through the packing machine during the conversion of the packing laminate to individual, filled packing containers. This can be realized normally without any major inconvenience. In the type of packing machine which manufactures aseptic packing containers intended to be filled with sterile contents the packing material web passes a bath or a chamber with sterilizing agent (usually hydrogen peroxide) which after it has sterilized the web is removed again with the help of mangle rollers or hot air. When the packing material web is provided with a cover strip placed on the outside thereof there is a risk that sterilizing agent which has penetrated in between the cover strip and the outside of the packing laminate is not completely removed, which is an obvious disadvantage.
An opening arrangement of the abovementioned type usually consists of a pouring opening provided in the packing laminate. The pouring opening is punched out during the manufacture of the laminate in its carrier layer, which customarily consists of paper. Thereafter, the carrier layer is coated with the required layers of thermoplastic material and aluminium foil and possibly further layers which will thus cover the punched-out hole in a water-tight manner. After the packing laminate thus has been completed the cover strip is applied to the outside of the laminate, whereupon the part of the cover strip located over the hole is joined by hotsealing to the thermoplastic layer which covers the pouring opening, so that it follows along and uncovers the pouring opening when the cover strip is removed from the finished packing container by the consumer.